Traditional AC/DC switched mode power supplies for the telecommunications industry follow a general design based around two individual cascaded power converters. The first power conversion stage typically performs the function of Power Factor Correction (PFC) and is almost exclusively based around a non-isolated boost converter topology. The second power conversion stage performs the functions of galvanic isolation and voltage transformation/control. A number of distinctly different circuit topologies have been successfully employed to perform the second stage of conversion. Some of the topologies that are commonly used are: Single switch forward converter, 2-switch forward converter, Half-bridge converter, and the Full-bridge converter. These converters may either employ hard or soft switching of the power switching transistors and/or diodes and all references to converters in this specification shall encompass either switching technique.
The different power converter topologies form a spectrum of design solutions with the simpler topologies best satisfying the requirements for low parts count in small power supplies, and the more complex topologies justifying their added complexity due to their improved performance in large power supplies.
A power supply manufacturer who provides a range of different power level solutions will therefore tend to face the need to develop a number of different product solutions, usually based on a range of different power conversion topologies. Each of these design solutions has its intendant engineering costs: design validation, compliance testing, production support, and product support. Any engineering solution that could result in a simple scalable product design can reduce this engineering cost as well as gaining volume-manufacturing efficiencies.
It is an object of this invention to provide a design that reduces the cost of design and provides a relatively simple and cost effective range of power supplies or to at least provide the public with a useful choice.